According to its latest numbers, Earnhardt is now No. 49 at $18.4 million — $12.6 in endorsements and $5.8 million in salary.

According to SI, all NASCAR drivers are taking a hit in the wallet. Four drivers made SI's top 50 last year — Jeff Gordon (18th), Tony Stewart (29th) and Jimmie Johnson (33rd) — but Earnhardt is the only driver on this year's list.

According to SI, Earnhardt's dip in earnings may be attributed to a loss of sponsorship or a decline in sponsorship dollars. Earnhardt's Hendrick Motorsports team does not have primary sponsorship for every race this season.

"Junior's endorsements are impressive for NASCAR, where the sponsorship dollars are drying up due to waning interest," SI says in its report. "Earnhardt, 38, wasn't even among the top 10 in winnings in 2012, but his off-track earnings are still the highest in the sport, thanks to deals with Diet Mountain Dew, Chevrolet, TaxSlayer.com, Nationwide Insurance, National Guard and Hellmann's."